1. Field of the Invention
The invention relates generally to techniques of playing a broadcast program content with enhanced security, and more particularly to improvements of techniques of playing a broadcast program content in an environment where a computer unit allows the broadcast program content to be viewed and/or listened to, with a tuner unit detachably coupled to the computer unit via an interface.
2. Description of the Related Art
In recent years, digital broadcasting has become more popular owing to satellite or terrestrial broadcasting. Digital broadcasting programs distributed by satellite broadcasting or the like are viewed and/or listened to, for example, in the following fashion:
Firstly, a radio wave is received by an antenna, and the received radio wave is frequency-converted by a converter. Secondly, the frequency-converted signal, after channel selection by a tuner, is decoded.
Thereafter, there is extracted from the decoded signal a transport stream (hereinafter, referred to as “MPEG2-TS”) which is in the form of a coded bit-stream compliant with the MPEG-2 standard. The extracted MPEG2-TS is formatted to contain various kinds of contents, such as images or still or moving pictures, sound, or program guides.
The MPEG2-TS, after decoded, is further converted to an analog signal, resultantly allowing a viewer to view and/or listen to a program content via an image output device such as a TV monitor or an LCD (Liquid Crystal Display) monitor and/or a sound output device such as a speaker.
In addition, it has been popular recently to add a tuner for reception of TV broadcast, on a personal computer (hereinafter, abbreviated as “PC”) in a detachable manner, to thereby allow a broadcast program content to be displayed on an LCD display of the PC for viewing, and allow a broadcast program content to be recorded in a storage device, such as an HDD (Hard Disk Drive), which is coupled to the PC, whether built-in or add-on.
In the industry of digital broadcasting, a broadcast program content is distributed in a digital format, without any significant reduction in picture and/or sound quality during signal propagation. This makes it easier to fully duplicate such a broadcast program content, which, in turn, runs the risk of copyright infringement.
In addition, it is general for a PC to easily accommodate various kinds of external devices by connection, at risk of illegal copying of a broadcast program content which has been received by the PC. Moreover, when a tuner and a PC are detachably coupled to each other, data indicative of a broadcast program content, during transmission from the tuner to the PC, is risky of being intercepted or tapped through an interface of the PC.
It has been that a broadcast program content is encrypted for providing copyright protection thereto, prior to reception by a PC from a tuner which has been detachably coupled to the PC.
This approach can prevent illegal viewing and duplication of a broadcast program content by virtue of encryption thereof, even if data indicative of the broadcast program content is tapped from an interface of a PC with a tuner, during transmission of the broadcast program content from the tuner to the PC. Japanese Patent Application Publication No. 2004-173027 discloses an exemplary conventional technique for encrypting a broadcast program content.